Antarctic krill is one of the most reliable large-scale sources of animal-derived protein-containing food. The catches of krill may well surpass the total level of fish catches in the whole world. The most valuable component of krill is its pure meat whose chemical composition is close to that of the meat of crabs and shrimps, and contains numerous valuable and vital amino-acids and microelements. However, for the meat of krill to be usable as food, it has to be completely separated from the shell.
Pure meat extracted or recovered from krill should have a minimum content of lipides, should be devoid of the remnants of the liver and of the contents of the gastrointestinal tract, the last of which affects the quality of the product and curtails its storage period.
When one considers that the krill-catching areas, more often than not, are far away from the bulk of the consumers, and that the transportation of krill takes considerable time for the same reason, the best solution is to treat krill directly where it is being caught, to obtain therefrom pure meat as a ready-to-use product, e.g. natural canned meat, or else as a semi-finished food, e.g. deep-frozen meat.
Known in the art is a method of separating the meat of crustaceans from the shell, including loading the crustaceans, forwarding them along a helical path, mechanically destroying the shell with aid of rotating discs with sharp burrs on their peripheries, and separating the meat from shell fragments by flotation.
With shrimps being treated by this known method, their meat is obtained as individual lumps; however, considerable deformation and disintegration of the meat lumps take place, which affects both the quality and appearance of the final product. Besides, the abovedescribed known method is usable for treating relatively large shrimp and is impractical for separating the shell of small crustaceans, e.g. krill. There is further known a method of separating the head of a shrimp from the body thereof by destroying the ties between the head portion and the body with a high-velocity flow of fluid. The essence of this method resides in a shrimp being positioned so that its head and body are introduced into a high-velocity water flow, the area of the connection of the head portion and the body being positioned adjacent to the edge of a stationary element. The effort being created by the high-velocity fluid flow is directed either at the head portion or the body of the shrimp, whereby the head portion and the body are separated.
The last-described method only separates the head portions of crustaceans from their bodies. The rest of the operations involved in breaking up the shell, extracting the meat and separating one from the other are performed by other methods. Thus, the last-described known method would not obtain pure meat, whereas the repeated operations of extracting the meat from the body and separating the components inflict inevitable losses and affect the taste of the final product on account of the latter's prolonged contact with a liquid.
The last-described method is likewise devised for treating relatively large shrimp and cannot be used for treating krill. Furthermore, the singular technique of treating shrimps essentially curbs down the productivity of the method.
There is also known a method of removing the shell of crustaceans, e.g. crabs (disclosed in the DE Pat. No. 2,430,095; Int. Cl..sup.2 A 22 C 29/02, published in 1976), including singular treatment of crustaceans by carrying them in an air flow past blade-like teeth and scrapers, in which way mechanical removal of the shell of crustaceans is effected.
The last-mentioned hitherto known method also includes classifying the crustaceans to be treated into fractions, indexing the crustaceans to be treated and treating them singularly within each fraction.
The above operations are labor-consuming, complicated and affect productivity.
Besides, the method does not provide for destroying such components as the liver and gastrointestinal tract, which does not enable production of pure meat. Furthermore, with the technique having been specifically devised for treatment of large crustaceans, it cannot be employed for treating antarctic krill.
Thus, the hitherto known methods of treating crustaceans, solving as they do the problem of obtaining edible products in different ways and to a different degree, cannot be employed for treating small crustaceans, e.g. antarctic krill. These methods are characterized by a limited ability of obtaining pure meat from the crustaceans. They do not provide an automated and highly productive process of treating small sea crustaceans.